The present invention relates to flexible shafts for transmitting rotational torque between a driving member and a driven member.
Power seats are a popular option on many vehicles sold today. The power seats typically are adjustable in the horizontal fore and aft and vertical directions as well as the seat back recliner movement to accommodate occupants of different height and size as well as to provide comfortable seating position to suit each occupant""s preferences.
Power seats typically have a frame for supporting a seat bottom cushion and a seat back cushion. The seat frame is mounted on a first and second spaced track assemblies each having an upper track which is connected to the seat support frame and which is slidably mounted on a lower track anchored to the vehicle floor. A drive mechanism typically includes a bidirectional motor which rotates a pair of drive shafts extending outwardly from the motor to a gear box mounted on each upper track. Typically, each gear box engages a lead screw extending longitudinally below each upper track. A drive block is mounted to each lower track and threadingly receives the lead screw to cause reciprocal, horizontal movement of the upper track and the attached seat frame upon selective activation of the drive motor.
Similar drive mechanisms are provided for vertical adjustment of the seat support frame and for angular adjustment of the seat back. The vertical drive mechanisms may also include front and rear edge drive mechanisms for selectively tilting the front and rear edges of the seat bottom independent of each other as well as simultaneously to raise and lower the entire seat or, in some applications only the seat bottom.
Each vertical and recliner drive mechanism includes a drive motor having a rotatable output shaft connected to a gear assembly either directly in the case of front and rear vertical drive mechanisms or by means of two shafts extending from a single motor to separate gear assemblies mounted on each upper track or on the seat support frame in the case of a seat recliner drive mechanism.
In order to span the many possible mounting locations, it is common to employ flexible cable formed of a wound stranded wire coupled at opposite ends to the drive motor or motor gear box and the lead screw gear box. The rotating cable is surrounded by a stationary flexible outer sheath or cover. A special retention device such as ferrule is disposed at each end of the cable housing cover to secure the cover to the respective gear box or motor.
While the use of this flex cable, motor and gear box arrangements has proven to work for its intended purpose, problems still exist. For example, excessive noise is generated at the flex cable ends and socket interface. The noise is generated by the surface of flex shaft ends contacting the inner surface of the socket.
Thus it would be desirable to provide a power seat adjuster which overcomes the problems associated with previous power seat adjusters using flexible drive cables. It would also be desirable to reduce objectionable noise generated by the engagement of the cable end surfaces with the inside surface of the sockets during activation of the motor.
In accordance with an aspect of the present invention a flexible shaft is provided having at least one end portion connectable to a socket. The at least one end portion has a substantially uniform cross-section defining a non-planar surface which is twisted about a reference axis for rotationally driving a cooperating planar surface in the corresponding socket.
In accordance with another aspect of the present invention the at least one end portion of the flexible shaft has a polygonal cross-section.
In accordance with another aspect of the present invention at least one end portion of the flexible shaft has a square cross-section.
In accordance with another aspect of the present invention the non-planar surface of the at least one end portion is twisted between 10 and 30 degree about the reference axis over an insertion length of the flexible shaft.
In accordance with another aspect of the present invention the flexible shaft is comprised of a plurality of steel strands wound about a center core.
In accordance with yet another aspect of the present invention, an assembly comprising a flexible shaft having at least one end portion and a socket for cooperating with the at least one end portion is provided. The at least one end portion has a substantially uniform cross-section defining a non-planar surface which is twisted about a reference axis for rotationally driving a cooperating planar surface in the socket.
In accordance with still another aspect of the present invention a power seat including a motor having a motor output for displacing a driven member, a gear mechanism having a gear mechanism input for transmitting a rotational torque from the motor to the driven member, a flexible drive shaft having at least one end portion for connecting to a socket associated with the at least one of the motor output and gear mechanism input, the at least one end portion has a substantially uniform cross-section defining a non-planar surface which is twisted about a reference axis for rotationally driving a cooperating planar surface in the corresponding socket.
The above features, benefits and advantages and other features, benefits and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken together with the accompanying drawings.